The implantation of stents has become standard medical practice for treatment of vessels or ducts constricted due to various stenotic pathologies. Although stents often relieve acute symptoms of a constriction, a major complication associated with all stents is progressive occlusion, which is variable and unpredictable, and can lead to sepsis, infarctions, or strokes. Unfortunately, the current methods for monitoring stent occlusion are inconclusive, indirect, or invasive; and most require expensive, in-patient diagnostic procedures. These shortcomings often lead to mistimed therapeutic actions: a preemptive and unnecessary stent replacement, or a post-symptomatic stent replacement combined with emergency anti-sepsis therapy. The objective of this proposal is to demonstrate the capabilities of a wireless, non-invasive, integrated system, which provides direct measurement of patency from inside a stent. Testing will be conducted using biliary stents, an application whose performance requirements are important for other stent applications such as TIPS, and coronary and ureteral stents. The research strategy to achieve this objective has four components: (1) further develop the technology for a sensing system based on a magnetoelastic resonant sensor integrated with the stent, and the associated wireless sensor interrogation electronics; (2) conduct in vivo testing and validation of the sensing system using integrated biliary stents implanted in porcine specimens; (3) develop an observable, controllable, and repeatable in vitro system that allows cells (either bacterial or endothelial) to culture on the sensors in an environment that replicates the implanted situation; (4) use the in vitro system to evaluate the performance of the sensors. The research will be conducted with full system verification in mind, including: endoscopic delivery; sensor biocompatibility; sub-chronic signal stability; sensor resolution, full scale range, and repeatability; and system accuracy, wireless range, and usability. The results of this research will demonstrate the applicability of the monitoring method to a wide range of stent types subjected to different restenotic pathologies. Important performance targets for the system include a full-scale range that includes a fully occluded stent, a resolution of less than 1 mm of patent diameter, and a wireless range of at least 7.5 cm. Successful demonstration of this system will lead to an inexpensive, real-time, outpatient procedure for directly monitoring stent occlusion. This will aid physicians in performing timely intervention, and will eliminate unnecessary invasive procedures in the course of post-implant care of stent patients. Ultimately, this will result in lower costs, fewer complications, and better outcomes. Further, regardless of the specific stent application, a wireless monitoring system with the sensitivity and spatial resolution targeted by this proposal can provide clinical researchers with a map of the progression of stent occlusion. This will result in an improvement in the efficiency of important clinical studies, and in the depth of knowledge gained by them.